Although their relationship was doomed to fall apart, I think people mistake whose fault it may be. Many people were saying it was Nagi’s fault for being indecisive, but he made it pretty clear several times he was only interested in Segawa (although circumstances were complicated for him). Rather it was Segawa who failed to push the relationship in any meaningful way, and in fact sabotaged it several times.
For example her friend group is made up of people who SOLEY want to date Nagi. Not only does she fail to force Nagi to draw lines between those girls and him, she actively encouraged him to focus on them instead of her (not a thing you do if you want to secure a guy). And then eventually when he inevitably runs into a conflict of interest because of the other girls advances, she just rolls over and accepts the results.
Nagi did all the pushing and gave her ample opportunities to escape her fate of an arranged marriage, but she just never made an effort. I think this was just a fling for her and there was nothing Nagi could do so long as he didn’t become said arranged fiancé, which was impossible due to his own forced arrangement.
